Nitrogen is an inert gas, which is often used in high temperature treatment of various materials or parts of the protective atmosphere. Therefore, impurities in nitrogen should be removed to a low level.
Generally speaking, when the oxygen content in nitrogen produced by nitrogen generator is less than 0.5%, Deoxidizer should be used for direct deoxidation; when the oxygen content is 0.5-3%, catalyst hydrogenation should be used for deoxidation; when the oxygen content is more than 3%, staged catalytic deoxidation can be used.
Because the oxygen content in nitrogen is too high, the amount of hydrogen required by stoichiometry is large, and there may be a risk of explosion when all the nitrogen is added at one time; And the heat released in the reaction is large, which is easy to burn the catalyst. Therefore, it is necessary to strictly control the amount of hydrogenation for staged deaeration. When the oxygen content in the feed nitrogen is too high, the feed gas can also be diluted with some pure nitrogen to make the oxygen content in the mixed gas less than 3%, and then the hydrogen catalytic deoxidation can be carried out.
The typical process flow of removing impurity oxygen by deoxidizer is: nitrogen passes through catalytic deaerator, water cooler, adsorption dryer and gas filter to get pure nitrogen product.
The typical process flow of hydrocatalytic deoxidization is adopted: firstly, appropriate amount of hydrogen is added into nitrogen (the addition amount is more than twice of the oxygen content in nitrogen), and then pure nitrogen product is obtained through catalytic deoxidizer (deoxidization), water cooler and adsorption in dryer (moisture removal) and gas filter (dust removal).
When the oxygen content in nitrogen is large, the staged hydrogenation catalytic deoxidation process can be used. Before the nitrogen enters the catalytic deoxidizer, the amount of hydrogenation should be strictly controlled, and a small amount of hydrogen is added into the catalytic deoxidizer 1 (primary deoxidization) for secondary deoxidization.
If the oxygen content in the nitrogen is high, the pure nitrogen should not have excessive hydrogen. At this time, the nitrogen purification unit adopts the method of hydrogenation catalytic deoxidation first, and then active copper oxide to purify nitrogen. The typical process flow is as follows: according to the oxygen content in the raw nitrogen, add a little excess hydrogen (according to stoichiometry), deoxidize it through the catalytic deaerator, and then remove the excess hydrogen in the nitrogen through electric heater and oxidation reaction. In addition to active copper oxide, silver molecular sieve can also be used as dehydrogenation agent.